This page lists IPS patch files for
RPG_RT.exe of
RPG Maker 2000/2003 that remove the battle-start that would normally occur from a random-encounter. Instead switch #1018 is activated as a signal, also variable #3355 receives the troop-ID the system has picked from the map's or area's troop-list.
Be sure to pick the right file for the exact version you are using or it will break your EXE. Files for 2003-1.09 work up to 2003-1.12 since all releases from 2003-1.10 on are official hacks. They also may be compatible in combination with Maniac Patch (this wasn't tested yet), but if, then only up to mp210414.
If you need to catch the switch or variable by event-page-condition, use the "MEPR"-version (means "MapEventPageRefresh") instead. The normal patch skips this process, though the switch can still be caught by CE-condition (or switch and/or variable through forks inside parallel code).
How can I change the IDs of switch and variable?
If you are skilled in hex-editing at least a bit, you can edit the DWORDs (signed Int32 LE) inside any of the IPS-files at offsets 0x29~0x2C (var) and 0x3C~0x3F (switch) before you apply the patches. I will (hopefully) add the addresses soon where to find them in an already patched RPG_RT.exe to change afterwards.